Tailoring Conductive 3D Porous Hard Carbon for Supercapacitors

Hard carbon has attracted great attention for energy storage owing to low cost and extremely high microporosity, however, hindered by its low electrical conductivity. The common strategy to improve the conductivity is through graphitization process which requires temperatures as high as 3000 °C and inevitably destroys the porous structure. Herein, a balance between the specific surface area and electrical conductivity in a 3D porous hard carbon by in situ iron‐catalyzed graphitization process together with the Si–O–Si network is successfully achieved. The Fe can accelerate the localized graphitization at relatively low temperature (1000 °C) to form nanographite domains with enhanced conductivity, while the Si–O–Si network contributes to generating a 3D porous structure. As a result, the optimized hard carbon exhibits a 3D interconnected and hierarchical porous structure with extremely high specific surface area (2075 m 2 g −1 ) and excellent electrical conductivity (12 S cm −1 ) which is comparable with that of artificial graphite. And thus, high capacitance of 315 F g −1 and excellent rate capability (174 F g −1 at 40 A g −1 ) are simultaneously achieved when used as electrodes for supercapacitors. The strategy is promising to build hard carbon materials with well‐tuned properties for high‐performance energy storage.